TCASII. Intruder aircraft overshot runway centerline.

Attributes
ACN	304592
Time
Date	199505
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sea
State Reference	WA
Altitude	msl bound lower : 3000 msl bound upper : 3000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : sea
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : cfi pilot : atp
Experience	flight time last 90 days : 150 flight time total : 7000 flight time type : 1500
ASRS Report	304592
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	conflict : nmac other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : took evasive action other other
Consequence	Other
Miss Distance	horizontal : 0 vertical : 200
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Descending on visual approach to runway 16L sea. Aligned on runway 16L centerline to the east of runway 16R. While switching from approach to tower, we noted a TCASII TA rapidly approaching from our 4 O'clock position. Almost immediately (and in short sequence) TCASII notification 'monitor vertical speed,' 'climb,' 'climb, climb now.' executed TCASII RA recovery procedure. Notified sea tower of our RA maneuver, both sea tower and an airliner flight responded that there was 'no conflict.' climb maneuver made a stabilized approach recovery impossible, flew a VFR missed and returned to visual runway 16R. During deplaning, a company pilot, who was seated at a window in the aft cabin, came up to tell us he observed the aircraft pass under us 'extremely' close. It appeared to overshoot runway 16R. We never saw it from the flight deck.

Original NASA ASRS Text

Title: TCASII. INTRUDER ACFT OVERSHOT RWY CTRLINE.

Narrative: DSNDING ON VISUAL APCH TO RWY 16L SEA. ALIGNED ON RWY 16L CTRLINE TO THE E OF RWY 16R. WHILE SWITCHING FROM APCH TO TWR, WE NOTED A TCASII TA RAPIDLY APCHING FROM OUR 4 O'CLOCK POS. ALMOST IMMEDIATELY (AND IN SHORT SEQUENCE) TCASII NOTIFICATION 'MONITOR VERT SPD,' 'CLB,' 'CLB, CLB NOW.' EXECUTED TCASII RA RECOVERY PROC. NOTIFIED SEA TWR OF OUR RA MANEUVER, BOTH SEA TWR AND AN AIRLINER FLT RESPONDED THAT THERE WAS 'NO CONFLICT.' CLB MANEUVER MADE A STABILIZED APCH RECOVERY IMPOSSIBLE, FLEW A VFR MISSED AND RETURNED TO VISUAL RWY 16R. DURING DEPLANING, A COMPANY PLT, WHO WAS SEATED AT A WINDOW IN THE AFT CABIN, CAME UP TO TELL US HE OBSERVED THE ACFT PASS UNDER US 'EXTREMELY' CLOSE. IT APPEARED TO OVERSHOOT RWY 16R. WE NEVER SAW IT FROM THE FLT DECK.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.